U.S. patent number 6,284,217 [Application Number 09/375,615] was granted by the patent office on 2001-09-04 for method and catalyst structure for steam reforming of a hydrocarbon.
This patent grant is currently assigned to Battelle Memorial Institute. Invention is credited to Anna Lee Y. Tonkovich, David P. Vanderwiel, Yong Wang.
United States Patent |
6,284,217 |
Wang , et al. |
September 4, 2001 |
**Please see images for:
( Reexamination Certificate ) ** |
Method and catalyst structure for steam reforming of a
hydrocarbon
Abstract
The present invention includes an improvement to the existing
method of steam reforming of hydrocarbon, wherein the improvement
comprises: the flowing is at a rate providing a residence time less
than about 0.1 sec resulting in obtaining product formation yield
or amount that is the same or greater compared to product formation
at a longer residence time. Another improvement of the present
invention is operation at a steam to carbon ratio that is
substantially stoichiometric and maintaining activity of the
supported catalyst. The present invention also includes a catalyst
structure for steam reforming of a hydrocarbon.
Inventors: |
Wang; Yong (Richland, WA),
Vanderwiel; David P. (Richland, WA), Tonkovich; Anna Lee
Y. (Pasco, WA) |
Assignee: |
Battelle Memorial Institute
(Richland, WA)
|
Family
ID: |
23481590 |
Appl.
No.: |
09/375,615 |
Filed: |
August 17, 1999 |
Current U.S.
Class: |
423/651; 252/373;
423/418.2; 518/702 |
Current CPC
Class: |
B01J
37/0244 (20130101); C01B 3/40 (20130101); C01B
3/38 (20130101); B01J 23/005 (20130101); B01J
2219/00835 (20130101); C01B 2203/0233 (20130101); Y02P
20/52 (20151101); C01B 2203/1011 (20130101); C01B
2203/1041 (20130101); C01B 2203/1064 (20130101); C01B
2203/1058 (20130101); C01B 2203/1082 (20130101) |
Current International
Class: |
C01B
3/40 (20060101); B01J 37/00 (20060101); B01J
37/02 (20060101); B01J 23/00 (20060101); C01B
3/38 (20060101); C01B 3/00 (20060101); C01B
003/26 (); C01B 003/32 () |
Field of
Search: |
;208/130 ;252/373
;518/700,702 ;423/418.2,651 ;48/214A |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2105253 |
|
Sep 1971 |
|
FR |
|
1003147 |
|
Oct 1962 |
|
GB |
|
Primary Examiner: Yildirim; Bekir L.
Attorney, Agent or Firm: Zimmerman; Paul W.
Claims
We claim:
1. A method for steam reforming of a hydrocarbon comprising:
reacting a mixture of steam and a hydrocarbon over a supported
catalyst at a temperature from about 650.degree. C. to about
900.degree. C.;
wherein said supported catalyst comprises a spinel support and a
catalyst metal;
wherein said step of reacting a mixture of steam and a hydrocarbon
is conducted at a residence time of less than about 0.1 second;
and
wherein said step of reacting results in at least about 50% of
hydrocarbon conversion and a CO selectivity of less than about
70%.
2. The method of claim 1 wherein said catalyst metal is selected
from the group consisting of rhodiun, iridium, nickel, palladium,
platinum, carbide of group VIb, and combinations thereof.
3. The method of claim 2 wherein the steam to carbon ratio is from
0.9 to 2.5.
4. The method of claim 2 wherein the hydrocarbon is a fuel selected
from the group consisting of gasoline, diesel and JP-8.
5. The method of claim 2 wherein the hydrocarbon is a selected from
the group consisting of alkanes, alkenes, alkynes, branched
isomers, aromatics, saturated and unsaturated hydrocarbons, and
combinations thereof.
6. The method of claim 2 wherein said step of reacting results in
about 50-95% of hydrocarbon conversion and a CO selectivity of
about 20-70%.
7. The method of claim 6 wherein the support comprises a magnesia
passivation layer.
8. The method of claim 6 wherein said support is made by a method
comprising impregnating alumina with a solution containing
magnesium.
9. The method of claim 8 wherein said catalyst metal comprises
rhodium.
10. The method of claim 9 wherein said mixture of steam and
hydrocarbon comprises water and methane.
11. The method of claim 2 wherein said mixture of steam and
hydrocarbon consists of water and methane.
12. A method for steam reforming of a hydrocarbon comprising:
reacting a mixture of steam and a hydrocarbon over a supported
catalyst at a temperature from about 600.degree. C. to about
1000.degree. C.;
wherein said supported catalyst comprises a spinel support and a
catalyst metal;
wherein said step of reacting a mixture of steam and a hydrocarbon
is conducted at a residence time of less than about 0.1 second;
wherein said mixture of steam and hydrocarbon has a steam to carbon
ratio of greater than about 0.9 and less than 2.5;
wherein said method is continuously conducted for over 40 hours;
and
wherein between about 26 hours time-on-stream and about 40 hours
time-on-stream, the CO selectivity remains essentially unchanged
and the hydrocarbon conversion changes less than about 5%.
13. The method of claim 12 wherein the steam to carbon ratio is
from 0.98 to 2, and
wherein said catalyst metal is selected from the group consisting
of rhodium, iridium, nickel, palladium, platinum, carbide of group
VIb, and combinations thereof.
14. The method of claim 13 wherein the hydrocarbon is a fuel
selected from the group consisting of gasoline, diesel and
JP-8.
15. The method of claim 13 wherein the hydrocarbon is a selected
from the group consisting of oxygenates, alkanes, alkenes, alkynes,
branched isomers, aromatics, saturated and unsaturated
hydrocarbons, and combinations thereof.
16. The method of claim 13 wherein, afier 40 hours of operation,
electron microscopy shows no coke deposits on the catalyst and BET
measurements detect no significant loss in surface area.
17. The method of claim 12 wherein the support comprises a magnesia
passivation layer.
18. The method of claim 13 wherein said support is made by a method
comprising impregnating alumina with a solution containing
magnesium.
19. The method of claim 18 wherein said catalyst metal comprises
rhodium.
20. The method of claim 19 wherein said mixture of steam and
hydrocarbon comprises water and methane.
21. The method of claim 20 wherein said mixture of steam and
hydrocarbon consists of water and methane.
Description
FIELD OF THE INVENTION
The present invention is a method and catalyst structure for steam
reforming of a hydrocarbon.
BACKGROUND OF THE INVENTION
Steam reforming of hydrocarbons is commonly used for feedstock
production for carbon-monoxide hydrogenation (Fischer-Tropsch
synthesis), methanol synthesis and hydrogen production. Steam
reforming is done commercially by flowing a mixture of steam and
the hydrocarbon past a supported catalyst having an alumina support
and a catalyst metal thereon, and reacting the mixture at a
temperature from about 600.degree. C. to about 1000.degree. C.,
forming at least one product. Research has been done with the
catalyst metal on a spinel support. Residence times are typically
on the order of seconds and steam tocarbon ratio greater than about
2.5. For steam to carbon ratio less than 2.5, catalyst activity is
generally degraded after hours to days due to coke formation and
the supported catalyst must be refreshed or replaced.
The rate of supported catalyst activity degradation has been
reduced by use of excess steam (steam to carbon ratio greater than
2.5). Excess steam, however, requires excess thermal energy and
results in large system pressure drop. Using less steam results in
faster degradation of catalyst activity because of coking from the
hydrocarbon(s).
Hence, there is a need for a method of steam reforming of a
hydrocarbon that provides greater product yield and permits using
less steam and maintaining catalytic activity of the catalyst.
SUMMARY OF THE INVENTION
The present invention includes an improvement to the existing
method of steam reforming of hydrocarbon, wherein the improvement
comprises:
the flowing is at a rate providing a residence time less than about
0.1 sec resulting in obtaining product formation yield or amount
that is the same or greater compared to product formation at a
longer residence time. Another improvement of the present invention
is operation at a steam to carbon ratio that is substantially
stoichiometric and maintaining activity of the supported
catalyst.
The present invention also includes a catalyst structure for steam
reforming of a hydrocarbon. The catalyst structure has
(a) a first porous structure with a first pore surface area and a
first pore size of at least about 0.1 .mu.m;
(b) a porous interfacial layer that is a spinel with a second pore
surface area and a second pore size less than the first pore size,
the porous interfacial layer having a thickness less than 4 mm
placed upon the first pore surface area;
(c) a steam reforming catalyst selected from the group consisting
of rhodium, iridium, nickel, palladium, platinum, carbide of group
Vlb and combinations thereof placed upon the second pore surface
area.
It is an object of the present invention to provide a method of
steam reforming of hydrogen with a residence time of less than
about 0.1 sec.
It is an object of the present invention to provide a catalyst
structure with a porous interfacial layer of spinel.
The subject matter of the present invention is particularly pointed
out and distinctly claimed in the concluding portion of this
specification. However, both the organization and method of
operation, together with further advantages and objects thereof,
may best be understood by reference to the following description
taken in connection with accompanying drawings wherein like
reference characters refer to like elements.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph of conversion and selectivity versus
temperature.
FIG. 2 is a graph of conversion and selectivity versus time.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
The present invention includes a method for steam reforming of a
hydrocarbon having the steps of flowing a mixture of steam and the
hydrocarbon past a supported catalyst having a support and a
catalyst metal thereon. The mixture is reacted at a temperature
from about 600.degree. C. to about 1000.degree. C. forming at least
one product. The improvement of the present invention is using a
spinel support and flowing the mixture at a rate providing a
residence time less than about 0.1 sec and obtaining product
formation that is the same or greater than that obtained at longer
residence times.
Also, under the previously described conditions, catalytic activity
is degraded when the steam to carbon ratio is substantially
stoichiometric. Another improvement of the present invention
realized by flowing the mixture at a rate providing a residence
time less than about 0.1 sec is maintaining activity of the spinel
supported catalyst beyond 6 hours without degradation by coking
even for substantially stoichiometric steam to carbon ratio.
Substantially stoiciometric is a steam to carbon content ratio
greater than about 0.9 and less than about 2.5, preferably from
about 0.98 to about 2.
The supported catalyst may be in the form of a powder of non-porous
particles, porous solid and combinations thereof.
Hydrocarbon includes oxygenates, alkanes, alkenes, alkynes,
branched isomers, aromatics, saturated and unsaturated hydrocarbons
and combinations thereof including fuels such as gasoline,
kerosere, diesel, JP-8.
EXAMPLE 1
An experiment was conducted to demonstrate the present invention.
The supported catalyst was spinel of a gamma-alumina
(.gamma.-Al.sub.2 O.sub.3) support with a magnesia (MgO)
passivation layer and rhodium oxide (Rh.sub.2 O.sub.3). The
approximate composition was about 15 wt% Rh.sub.2 O.sub.3, about 5
wt% MgO, and about 80 wt% .gamma.-Al.sub.2 O.sub.3. The supported
catalyst was prepared by (1) calcining a high surface area
.gamma.-Al.sub.2 O.sub.3 at 500.degree. C. for 5 hours; (2)
impregnating the .gamma.-Al.sub.2 O.sub.3 with MgO using the
incipient wetness technique with a solution of magnesium nitrate;
and obtaining an MgO modified .gamma.-Al.sub.2 O.sub.3 support; (3)
drying the modified support at 110.degree. C. for 4 hours followed
by (4) a second calcination at 900.degree. C. for 2 hours; (5)
impregnating the modified support with Rh.sub.2 O.sub.3 with the
incipent wetness technique from a rhodium nitrate solution; (6)
followed by a final drying 110.degree. C. for 4 hours and a (7) a
final calcination at 500.degree. C. for 3 hours to obtain a powder
of the supported catalyst.
A microreactor was constructed of a quartz tube with 4 mm ID and
6.35 mm OD. About 0.2 g of powder of supported catalyst was placed
in the microreactor in a packed bed arrangement.
Reactants were steam and methane in a steam to carbon ratio of
approximately 1 which is stoichiometric within measurement
uncertainty. Reactants were flowed through the reactor at
temperatures from 650.degree. C. to 900.degree. C.
Results are shown in FIG. 1 for a steam to carbon ratio of 3 with
conversion ranging from about 52% to 95% with increasing
temperature and selectivity ranging from 22% to 70%.
Results in FIG. 2 are for a steam to carbon ratio of 1 at
900.degree. C. over 40 hours. No degradation of the supported
catalyst was observed. Electron microscopic examination after
testing revealed no coke deposition and BET measurements detected
no significant loss in surface area.
CLOSURE
While a preferred embodiment of the present invention has been
shown and described, it will be apparent to those skilled in the
art that many changes and modifications may be made without
departing from the invention in its broader aspects. The appended
claims are therefore intended to cover all such changes and
modifications as fall within the true spirit and scope of the
invention.
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